Written By hannah hollinger
Published: 08/07/2020Updated: 09/08/2020
Seresto for Dogs | Wag!

Seresto for dogs is an odorless collar worn to kill fleas and ticks on contact with your pet’s skin. The collar protects your dog for 8 months against fleas and ticks, and although rare occurrences, mites, and biting lice.

Seresto is veterinarian-approved and is safe for use on puppies and dogs over the age of 7 weeks. Keep reading to learn more about this innovative anti-parasitic collar.


Collar sizes are described as a weight band of up to 18 pounds for small dogs, and over 18 pounds for large dogs.

  • One 38cm collar (12.5g) contains imidacloprid 100mg/g and flumethrin 45mg/g

  • One 70cm collar (45g) contains imidacloprid 100mg/g and flumethrin 45mg/g

The active ingredient imidacloprid works on the central nervous system of insects. The flumethrin is a synthetic ectoparasiticide that causes paralysis and death in insects.

Dosage instructions

Remove the collar from the protective bag. Unroll the collar and place on your dog’s neck, making sure that you can insert 2 fingers between your dog’s neck and the collar. Cut off any excess beyond 2cm once you have pulled the collar through the closure loop. Wear continuously for 8 months and check the tightness periodically.


While studies do not give the efficacy of Seresto for dogs against mites and lice, the collar is highly effective for the eradication of ticks and fleas. Protection against ticks averaged 90%. For fleas, the result showed a 95% efficacy.

While the effect on fleas takes place within 24 hours, it works against ticks in 6 hours. However, it is recommended that you remove any ticks you see on your dog when applying the collar to try and avoid the transmission of a tick-borne disease.

The collar has a sustained release technology that allows the continued release of the ingredients over time, which means coverage for the full 8 months. The Seresto collar is water-resistant, and occasional contact with water does not affect the efficacy of the collar.

Side effects

The side effects seen with this collar are rare and typically mild.

  • Dogs may present with hair loss and mild skin reactions like scratching and redness that should clear up within 1 or 2 weeks

  • In rare cases, inflammation, eczema, dermatitis, or lesions may occur (temporary removal of the collar may be required)

  • Your dog may twitch occasionally for a few days, but this is due to the newness of having the collar, not a chemical reaction

  • If your dog chews and swallows some of the collar, there may be gastrointestinal symptoms like loose stool


Do not use the collar on dogs under 7 weeks of age. The appropriate sized collar must be used according to your dog’s weight. Other considerations are:

  • The collar is water-resistant and will remain effective under normal conditions

  • Dogs wearing the collar shouldn’t be bathed more than once a month, and a soap-free shampoo should be used

  • Dogs who swim more than once a month the duration of effectiveness may be reduced to 7 months for ticks and 5 months for fleas

Drug interactions

Although there are no known drug interactions with Seresto collars, it is essential that you discuss the use of the collar with your vet. If there are supplements, natural therapies, or vitamins in your dog’s daily regimen, let your veterinarian know. 

Allergy reactions and sensitivity

  • Do not use on puppies under 7 weeks of age

  • The safety of Seresto for dogs (flumethrin and imidacloprid) has not been verified with pregnant and lactating dogs

  • Do not use if your dog has shown previous sensitivity to flumethrin, imidacloprid, or other ingredients within the same chemical family 

  • People with a sensitivity to the ingredients should not handle the collar

  • Store the collar away from children and animals

Frequently asked questions

How does Seresto for dogs work?

The active ingredients are released in controlled, low doses that work on your dog’s skin and coat, preventing parasitic invasion for an extended period.

Do I need a prescription for a Seresto dog collar?

The Seresto collar is recently available for sale on the Internet. However, purchasing from your vet ensures safe and proper usage instructions. As well, you know that you are getting a collar produced within the guidelines of veterinarian approval. 

Why am I still seeing a tick on my dog even with the collar?

Ticks may still jump on your dog, but once they contact the fur, they will be exposed and affected by Seresto for dogs and die.

My dog has chewed the collar. What do I do?

Your dog should only experience mild gastrointestinal upset if the collar is chewed. If your pet had ingested the entire collar, please contact the veterinarian. The collar should be periodically checked and adjusted as necessary over the 8 months.

Do I have to stretch the collar to activate it?

Although many collars require stretching for activation, the unique and highly effective formulation of the Seresto collar for dogs does not require that to be effective. 

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© 2024 Wag Labs, Inc. All rights reserved.